Oblate versus Prolate Electron Density of Lanthanide Ions: A Design Criterion for Engineering Toroidal Moments? A Case Study on {Ln } (Ln=Tb, Dy, Ho and Er) Wheels.

We report four new complexes based on a {Ln } wheel structure, three of which possess a net toroidal magnetic moment. The four examples consist of {Tb } and {Ho } wheels, which are rare examples of non Dy based complexes possessing a toroidal magnetic ground state, and a {Dy } complex which improves its toroidal structure upon lowering the crystallographic symmetry from trigonal (R ) to triclinic (P ). Notably the toroidal moment is lost for the trigonal {Er } analogue. This suggests the possibility of utilizing the popular concept of oblate and prolate electron density of the ground state M levels of lanthanide ions to engineer toroidal moments.